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PubMed1996

The recognition potential and conscious awareness.

The idea that conscious awareness of a recognizable image is necessary for it to evoke the recognition potential (RP) was tested by asking bilingual subjects to selectively attend to superimposed English and Chinese word images. The subjects detected most of the words in the attended language, but were largely oblivious of words in the non-attended language. Attended word images evoked the RP. Non-attended words did not. RP latency was less for Chinese than for English words. This provided a basis for inferring which language a subject was trying to read when valid English and Chinese words were both present. A subject was looking for Chinese if the latency was short and for English if it was long. The results showed that selective attention had a powerful effect on the RP. They supported the idea that conscious awareness is necessary for evoking it, though they did not rule out the theoretical possibility that some method not yet tested could be found that would block conscious awareness without blocking the RP. The sensitivity of the RP to what a subject is trying to see and its low variance seem to provide advantages for studying visual perception. It provides a short latency indicator of image processing that merits further investigation. Use of it may lead to a better understanding of visual perceptual processes.

Adult↗
PubMed1990

Ritanserin decreases portal pressure in conscious and unrestrained cirrhotic rats.

We have recently demonstrated that ritanserin, a serotonin 5-hydroxytryptamine receptor antagonist void of systemic effects, caused a significant reduction of portal pressure in conscious cirrhotic dogs. The mechanism by which ritanserin lowers portal pressure is poorly defined. We investigated the splanchnic and systemic hemodynamic effects of ritanserin (0.63 mg/kg body wt i.v., a dose known to completely inhibit binding of 5-hydroxytryptamine to its receptors), in conscious and unrestrained cirrhotic rats (n = 13). Heparinized catheters were placed into the portal vein, inferior vena cava, aorta, and left ventricle with exit from the neck. Hemodynamic studies were performed 4 h after consciousness was regained. Cardiac output and regional blood flows were measured using radiolabeled microspheres and the reference sample method. Sixty minutes after administration, ritanserin caused a significant reduction of portal pressure (-17%) with minimal changes in portal venous inflow (+3%). Portal vascular resistance decreased significantly (-23%), whereas splanchnic arteriolar resistance was similar before and after ritanserin. A significant increase in mean arterial pressure (+5%) and cardiac output (+22%) was observed. Our results suggest that ritanserin lowers portal pressure through a mechanism separate from portal venous inflow. This effect could be due to changes in intrahepatic or on portocollateral resistances, or both. These findings support the potential use of this new agent in the treatment of portal hypertension.

Animals↗
PubMed1993

Assessment and communication of conscious level: an audit of neurosurgical referrals.

Telephone referrals of 100 head-injured patients to a neurosurgical service were assessed to determine if altered consciousness was adequately described by the referring doctor. Of the patients, 60 per cent were resuscitated, assessed and referred by SHOs. Only 30 per cent of doctors were fully conversant with the Glasgow Coma Scale and 18 per cent were unable to describe altered consciousness. Assessment of motor response was often described inaccurately and this was frequently due to the use of an inappropriate stimulus. The use of a pictorial guide to motor responses and a 'Head Injury Proforma' are suggested as means of improving referral and enhancing audit. The majority of doctors had not received formal training in the assessment of conscious level during their undergraduate or postgraduate training. Training video tapes from neurosurgical units showing standard examination methods and typical responses would allow self-assessment and training.

Adolescent↗
PubMed1984

Effects of indomethacin on blood flow in the normal pancreas in conscious dogs.

In anesthetised animals basal pancreatic blood flow, both in the normal gland and in acute pancreatitis, and basal renal blood flow have been shown to be dependent on prostaglandins (PGs). However, in conscious dogs it has been demonstrated that the reliance of basal renal blood flow on PGs is only apparent, and probably due to the effect of anesthesia and surgery stimulating PG synthesis through enhanced stimulation of the sympathetic nervous system. This study was undertaken to investigate the changes in mean blood pressure, cardiac output, and pancreatic arterial blood flow, relative to the cardiac output, in the normal pancreas, with and without PG synthesis inhibition (indomethacin) in conscious dogs. Blood flows were measured with electromagnetic flow probes. The effects of indomethacin were measured over a 2-hr period and compared to a control group. The results show that the relative pancreatic blood flow is not affected by doses of indomethacin which decrease cardiac output (P less than 0.5). It is suggested that PGs may have no effect on blood flow in the normal pancreas in conscious animals.

Animals↗
PubMed1977

Effects of uneven elastic loads on breathing pattern of anesthetized and conscious men.

In anesthetized subjects rib cage strapping (RCS) did not change tidal volume (VT) and increased ventilation (V), whereas abdomen strapping (AS) markedly decreased VT and V. Both kinds of strapping decreased expiratory duration (TE), but did not change inspiratory duration (TI) and breathing rate. RCS and AS decreased lung volume by about 200 ml and increased the elastance of the repiratory system by 12 cm H2O/1 and 9 CM H20/l, repectively. The changes produced are mainly due to mechanical factors, although reflexes also seem to be operating in some cases. In conscious subjects RCS decreased VT, TI, TE and did not change V, whereas AS did not change these parameters. The different changes in conscious and anesthetized subjects show the effects of cortical influences, which also partly explain the differen effects elicited in conscious subjects by RCS and AS. The effects produced by RCS are mainly due to the sensation of hindrance to rib cage expansion, rather than to that of rib cage squeezing, as shown by experiments of RCS without reduction of rib cage volume.

Abdomen↗
PubMed1987

Vagal and sympathetic components of the heart rate range and gain of the baroreceptor-heart rate reflex in conscious rats.

Previous studies in conscious rats have examined the relationship between mean arterial pressure (MAP) and heart rate (HR) only during relatively small or unidirectional changes in blood pressure. We have now examined this relationship more fully in conscious Sprague-Dawley rats using graded bolus i.v. doses of phenylephrine and nitroprusside to alter MAP over a range of 60-160 mm Hg with a view to determining the contribution made by the vagus and sympathetic (after atenolol or methylatropine, respectively). In 25 rats the relationship of HR to MAP followed a sigmoidal rather than a linear function (P less than 0.001) with clear upper and lower HR plateaus. The HR range estimated from a logistic equation was 217 +/- 7 b/min while the average gain between the inflection points was 4.1 +/- 0.2 b/min/mm Hg (1.8 times greater than from a linear fit). The vagus makes a greater contribution to the HR range than the sympathetic (61 vs 39%, respectively) while the converse is the case for the gain (46% vagus, 63% sympathetic). In the presence of both blocking drugs, changes to HR were less than 7% of control. These results suggest that the baroreceptor-HR reflex in the conscious rat is best characterised by a sigmoid curve with approximately equal contributions from both the cardiac vagus and the sympathetic nerves.

Animals↗
PubMed1987

Cardiac receptors affect regional flow during acute infarction in conscious rats.

This study was conducted to determine if cardiac receptors have a role in the control of the regional circulations during small acute myocardial infarction in the conscious rat. Cardiocirculatory dynamics and cardiac output distribution (microspheres) were measured in conscious rats 24 and 48 h after surgery for left main coronary artery ligation or the sham procedure. Data from animals without treatment were compared to data from animals treated to induce chemical cardiac denervation (85% phenol applied to the supraventricular surface of the heart and the root of the great vessels). The results suggest that neurogenic vasopressor stimuli originating from the heart contribute to changes in peripheral resistance secondary to small, acute, experimentally induced myocardial infarction in the conscious rat.

Animals↗
PubMed1989

Renal sympathetic responses to changes in arterial pressure in conscious rabbits.

Renal sympathetic nerve activity (RSNA) at rest and in response to changes in mean arterial pressure (MAP) were examined by measuring norepinephrine (NE) spillover rate across the kidney in 14 conscious rabbits. NE spillover rate was calculated from veno-arterial difference in plasma NE concentrations across the kidney corrected by the fractional extraction of infused tritiated NE. Renal NE spillover rate (mean +/- S.E.M.) at rest in 14 conscious rabbits was 14.7 +/- 0.9 ng/min. During sodium nitroprusside infusions at 10 and 20 micrograms/kg/min, renal NE spillover rate significantly increased by 55 and 101% in response to falls in MAP of 15 and 19% respectively. During phenylephrine infusion at 2 micrograms/kg/min, renal NE spillover rate significantly decreased by 40% in response to a 14% rise in MAP. The relative contribution of renal to total NE spillover rate decreased during sympathetic stimulation, while this ratio was unchanged during sympathetic inhibition. This study demonstrates that the renal NE spillover method is sufficiently sensitive and reliable to detect the responses in RSNA to physiological stimuli in conscious rabbits. The difference observed in the degree of stimulation of renal versus total NE spillover rate during hypotension produces confirmation that sympathetic responses are not uniformly distributed in the body.

Animals↗
PubMed1986

The role of anger in the consciousness development of peace activists: where physiology and history intersect.

The focus of this paper concerns the role of anger in the development of consciousness in peace activists. By looking at this from 3 perspectives we can see an intersection of physiology and history. Looked at most closely, anger is a physiological event that recurs in the life of an individual. From a broader perspective, anger plays a critical role and a particular step in the development of consciousness. And from the broadest perspective, we may see how individual peace activists play a role in history by helping to resolve those contradictions (such as the present one between war and peace) by which history jerks its way forward. To put the proposition most carefully, it will be argued that anger is the personal fuel in the social motor that resolves the institutional contradictions that arise in the course of history. The materials on which this paper is based come from two sources. First is the study I have conducted in recent years on the development of consciousness in peace activists. Wishing to contribute my scientific skills to the peace movement, I have analyzed autobiographies of famous peace activists and oral histories of contemporary activists in Connecticut where I live. Since results from both the autobiographies and the oral histories are similar for present purposes, I will not make any distinction between them. The second source of material is the work that I and other researchers have conducted for many years on the brain mechanisms, behavioral complexities and evolutionary trends of aggressive behavior in rats, cats and monkeys. This material has been extensively published and is referred to in the bibliography (Adams, 1979, 1980).

Aggression↗
PubMedDate not supplied

Hemodynamic actions of endothelin in conscious and anesthetized dogs.

The newly described endogenous peptide, endothelin, was administered to five chronically instrumented conditioned dogs. Endothelin produced significant and simultaneous increases in both heart rate (HR) and mean arterial pressure (MAP) in conscious dogs. Endothelin also produced significant increases in MAP in anesthetized animals. Ganglionic suppression induced by hexamethonium (10 mg/kg) and atropine (0.1 mg/kg) blocked HR responses and markedly inhibited the pressor responses to endothelin in conscious animals. These results suggest that endothelin in part acts to elevate blood pressure and heart rate through modification of autonomic nervous system tone. When endothelin and angiotensin II were administered in mole equivalent doses, angiotensin II produced a pressor response of greater magnitude than did endothelin in conscious animals.

Anesthesia, General↗
PubMedDate not supplied

Endothelin produces systemic vasodilation independent of the state of consciousness.

The effects of endothelin, ET-1, on pulmonary and systemic hemodynamics were studied in the open chest dog and changes in systemic arterial pressure in dogs under conscious and anesthetized states were compared. Rapid intravenous (IV) bolus injections of ET-1, 100-1,000 nanograms/kg, significantly decreased systemic arterial pressure, and significantly decreased systemic vascular resistance whereas left atrial pressure and pulmonary vascular resistance were not altered. Reductions in systemic arterial pressure in response to bolus injection of ET-1, 100 and 300 nanograms/kg IV, during conscious state and during anesthesia were similar, respectively. The present data suggest that ET-1 dilates the systemic vascular bed independent of the animal's state of consciousness. The present data also suggest that when compared to the systemic vascular bed, the pulmonary vascular bed is less responsive to bolus administration of ET-1.

Anesthesia, General↗
PubMed1994

A new method for continuous measurement of regional cerebral blood flow using laser Doppler flowmetry in a conscious rat.

We have developed a new system to continuously measure regional cerebral blood flow (rCBF) in the cortex of a conscious animal. For this purpose, we used rats and laser Doppler flowmetry. Under pentobarbital anesthesia, the animal's skull was opened making a small square hole 3 mm x 3 mm in size. A transparent acrylic plate was placed over the hole in the skull. A polyethylene cannula (inner diameter 1.0 mm, length 5.0 mm) was fixed on the plate as a guide for the laser Doppler flowmeter (LDF) probe (outer diameter 1.0 mm, length 5.5 mm). Both the plate and guide cannula were fixed to the skull by dental cement. Every day for the following two weeks after surgery, the conscious animal was placed in a hammock for recording rCBF. A LDF probe was freely attachable to the plate above the cortex via the guide cannula during measurement of rCBF. The rats were kept in a hammock with their legs firmly touching the floor during measurement of rCBF. It was possible to measure rCBF every day for about two weeks, and rCBF responded consistently to inhalation of 7% CO2 when the responses were expressed as percentages of the prestimulus control rCBF values. This system is recommended for the continuous measurement of rCBF in a conscious animal.

Animals↗
PubMed1992

The acute effects of MK-801 on cerebral blood flow and tissue partial pressures of oxygen and carbon dioxide in conscious and alpha-chloralose anaesthetized rats.

The dynamic effects of the non-competitive N-methyl-D-aspartate receptor antagonist, MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine] , on cerebral blood flow and tissue partial pressures of oxygen and carbon dioxide were investigated in the striatal and occipital regions of conscious and anaesthetized rats by mass spectrometry. MK-801 (0.5 and 5 mg/kg, i.p.) induced a large increase in the blood flow of both cerebral regions of conscious rats, without significant changes in local tissue partial pressures of oxygen and carbon dioxide. The increase in cerebral blood flow was maximal within 30 min after injection. Its amplitude was independent of the dose of MK-801, but cerebral blood flow remained elevated for up to 4 h after 5 mg/kg MK-801, while it progressively decreased towards its basal level in rats given 0.5 mg/kg MK-801. The amplitude and time-course of the vascular changes were similar in the two cerebral regions studied. The difference in the changes in tissue partial pressure of oxygen induced by MK-801 and by a 6% CO2 inhalation suggests that the MK-801-induced rise in cerebral blood flow in conscious rats is, at least partly, due to an increase in oxidative metabolism. In contrast, MK-801 induced either no changes or decreases in cerebral blood flow in alpha-chloralose-anaesthetized rats. The present results should be taken into account not only to determine the mechanisms by which N-methyl-D-aspartate receptor antagonists may exert their neuroprotective effects but also to further elucidate the sites of action of MK-801 in the central nervous system.

Anesthesia, General↗
PubMed1991

Consciousness and synchronicity.

The brain is described as a system whose states are subject to quantum uncertainty. Conscious observation brings individual states into being from the multiple states possible at a given instant. This gives rise to information, which is the content of consciousness. Synchronicity is the principle by which a single state is generated by conscious observation throughout the brain at a given instant. It is the equivalent of the non-local interaction in quantum theory. Both psychodynamic and cognitive applications of the proposed model are described.

Cognition↗
PubMed1989

Prolonged abnormalities of left ventricular diastolic wall thinning in the "stunned" myocardium in conscious dogs: time course and relation to systolic function.

Myocardial reperfusion after reversible ischemia is known to be associated with prolonged abnormalities of systolic contractile function (myocardial "stunning"). However, no information is available regarding the recovery of diastolic function in the stunned myocardium in the conscious state. Accordingly, 10 conscious dogs instrumented with pulsed Doppler thickening probes underwent a 15 min occlusion of the left anterior descending coronary artery followed by 7 days of reperfusion. Regional systolic function was assessed as net systolic thickening fraction. Left ventricular regional diastolic properties were estimated from two variables: the mean rate to half end-diastolic thinning and the late diastolic thinning fraction. Both indexes of diastolic function remained severely impaired after restoration of flow. In general, the recovery of the mean rate to half end-diastolic thinning and of the late diastolic thinning fraction paralleled the recovery of systolic thickening, but the impairment of the mean rate to half end-diastolic thinning was more marked than that of the late diastolic thinning fraction. At 4 h of reperfusion, the values for the mean rate to half end-diastolic thinning and the late diastolic thinning fraction (expressed as percent of baseline) were 57 +/- 5% (p less than 0.001 versus baseline) and 79 +/- 7% (p less than 0.05), respectively, whereas systolic thickening fraction averaged 52 +/- 10% (p less than 0.001). At 24 h, the mean rate to half end-diastolic thinning and the late diastolic thinning fraction were no longer significantly different from baseline, whereas systolic thickening fraction remained decreased at 82 +/- 4% (p less than 0.001) and returned to control values by 48 h. This study demonstrates the presence of profound, prolonged abnormalities of regional diastolic wall thinning after a brief episode of ischemia in the conscious state and expands the concept of myocardial stunning from the traditional notion of impaired systolic performance to that of a global derangement in mechanical function that involves both systolic and diastolic properties.

Animals↗
PubMed1994

Neurobiology of conscious experience.

Recent research and theory suggest that conscious experience involves a modelling process. The human brain generates an internal model to fit incoming information about the external world, and experiences the model rather than the information. The modelling occurs at the level of the neocortex and may be associated with specific oscillatory field potentials. Imagining exercises the modelling system independently of sensory information. General disorders of consciousness are caused by damage to those areas of the brain that energize and direct the modelling process Specific deficits of consciousness are caused by focal lesions to sensory or motor cortex that prevent the modelling of particular input and output patterns.

Attention↗
PubMed2005

Testosterone reduces unconscious fear but not consciously experienced anxiety: implications for the disorders of fear and anxiety.

BACKGROUND: The fear-reducing properties of testosterone have been firmly established in animals but not in humans. However, human data on the relation between testosterone, fear, and anxiety have predominantly involved questionnaires that index cortically executed conscious appraisal of anxious mood. Animal studies, on the other hand, indicate that the effects of testosterone on motivation and emotion are of subcortical origin and of unconscious nature. Presently, it was hypothesized that a single testosterone administration to humans would reduce unconscious fear but not consciously experienced anxiety. METHODS: In a placebo-controlled, double-blind crossover design, a single dose of testosterone (.5 mg) or placebo was administered to 16 healthy female volunteers. Afterward, a masked emotional Stroop task measured unconscious emotional responses to fearful faces, while multiple self-reports of mood indexed consciously experienced anxiety. RESULTS: As hypothesized, the habitual vigilant emotional response to the masked fearful face observed in the placebo condition was significantly reduced after testosterone was administered, while the self-reported measures of anxiety remained unaffected. CONCLUSIONS: These data provide the first direct evidence for fear-reducing properties of testosterone in humans. Furthermore, by dissociating specific aspects of fear and anxiety in humans, this outcome highlights that testosterone's effects on motivation and emotion concern the subcortical affective pathways of the brain.

Adult↗
PubMed2005

Does consciousness really collapse the wave function? A possible objective biophysical resolution of the measurement problem.

An analysis has been performed of the theories and postulates advanced by von Neumann, London and Bauer, and Wigner, concerning the role that consciousness might play in the collapse of the wave function, which has become known as the measurement problem. This reveals that an error may have been made by them in the area of biology and its interface with quantum mechanics when they called for the reduction of any superposition states in the brain through the mind or consciousness. Many years later Wigner changed his mind to reflect a simpler and more realistic objective position which appears to offer a way to resolve this issue. The argument is therefore made that the wave function of any superposed photon state or states is always objectively and stochastically changed within the complex architecture of the eye in a continuous linear process initially for most of the superposed photons, followed by a discontinuous nonlinear collapse process later for any remaining superposed photons, thereby guaranteeing that only final, measured information is presented to the brain, mind or consciousness. An experiment to be conducted in the near future may enable us to simultaneously resolve the measurement problem and also determine if the linear nature of quantum mechanics is violated by the perceptual process.

Animals↗